The present invention relates to a novel and improved press and particularly relates to a press of the type useful for embedding toothed connector plates into the joints of wooden trusses and the like.
The building construction industry has recently made tremendous strides forward with the advent of prefabricated wooden trusses, panels, and the like. Such trusses comprise wooden framing members, in most cases, fastened together at their joints by nail plates, for example, of the type disclosed in U.S. Pat. No. 2,877,520 of common assignee herewith. A number of methods for applying the nail plates to the butt joints, such as hand nailing, utlizing individual power-operated presses at each joint, etc., have variously proven time-consuming, laborious, expensive, and not susceptible to large-scale automated truss fabrication techniques.
Truss fabrication techniques have advanced to the state where power-operated presses for embedding the nail plates into the joints of the wooden frame members are utilized. One such truss fabrication technique provides for the prepositioning of the frame member on a jig table in the pattern of the truss with the connector plates spotted on opposite sides of the joints of such members. Thereafter, the connector plates are pressed into the joints to fasten the frame members together and form a completed truss, panel, or the like. Presses capable of providing the foregoing action are disclosed in U.S. Pat. Nos. 3,079,607 and 3,195,449 of common assignee herewith.
In U.S. patent application Ser. No. 867,730, filed Oct. 20, 1969 now U.S. Pat. No. 3,603,244 dated Sept. 7, 1971, of common assignee herewith, there is disclosed a toggle-actuated press mounted for movement along a track and a control system for periodically stopping the press in a pressing position with the press platen located over the connector plates of the joints of the wooden members. The press of that application is disclosed more fully in U.S. Pat. No. 3,520,252, issued July 14, 1970, also of common assignee herewith. While the press disclosed in that application and patent has operated satisfactorily, particularly where the loadings across the press are substantially uniform, asymmetrical loadings have caused problems. Asymmetrical loadings are caused by the differences in location of the joints of the various types and sizes of trusses. Further, in those presses which mount fluid-actuated cylinders at their opposite ends, for example, the presses disclosed in U.S. Pat. Nos. 3,079,607 and 3,195,449, only the cylinder or the cylinders at one end of the press are generally effective with respect to the eccentric load. Consequently, these presses are limited in capacity when subjected to asymmetrical loadings to substantially the capacity of the cylinder or cylinders at one end of the press.
In U.S. Patent Application Ser. No. 190,724, filed Oct. 20, 1971, now U.S. Pat. No. 3,750,562, dated Aug. 7, 1973 of common assignee herewith, there is disclosed a press having a fluid actuated cylinder at each end of the press and connecting between the press base and the press head, with suitable guides provided at opposite ends of the press. When the press is subjected to asymmetrical loadings, the unused pressing capacity at one end of the press is transferred to its opposite end to provide a uniform loading along the entirety of the press by use of a load transfer apparatus. The load transfer apparatus interconnects the opposite ends of the press and includes at each end a bell crank pivotably mounted to the base and a pair of rods pivotably connected at opposite ends to the bell crank and to the moveable press head. A transfer bar interconnects the bell cranks at opposite ends of the press. When asymmetrical loadings are encountered, the force applied by the cylinder at the unloaded or partially loaded end of the press is transferred to the loaded end through the rod, bell cranks and transfer bar.